St. John's wort extracts can be as effective as standard antidepressant drugs for treating mild to moderate major depression, with significantly fewer side effects. However, recent ConsumerLab.com tests revealed that six of ten St. John's wort supplements tested contained lower levels of key plant compounds than expected. These compounds, hypericins and hyperforin, are associated with the herb's effectiveness. In a suggested daily serving, ConsumerLab.com found amounts of hypericins and hyperforin ranged across products by more than 2,000% and 20,000%, respectively.

"The wide variation across products means that some St. John's wort supplements may be helpful for depression, while others may not contain enough of the herb to have a meaningful effect," said ConsumerLab.com President Tod Cooperman, MD. The high failure rate may be attributable to adulteration of St. John's wort extracts with dyes that resemble St. John's wort when tested using some analytical methods.

ConsumerLab.com tested products using a method which identifies the hypericin molecule and is not "tricked" by dyes. The FDA does not specify which methods manufacturers must use to verify the quality of ingredients and supplements. Supplements were also tested by ConsumerLab.com for potential contamination with the heavy metals arsenic, cadmium and lead and pills were checked to be sure they would break apart properly to release their ingredients.

ConsumerLab.com was able to identify four St. John's wort supplements which passed all of its quality tests and it identified a "top pick" among them.

ConsumerLab.com's St. John's Wort Supplements Review is now available online here.

The report summarizes the clinical evidence regarding the use of St. John's wort, including differences between forms (extracts and herb powders), dosage, what to look for on labels, possible side-effects, and potential drug interactions.